I've got a completely stock 390 4V in the '69 Mach 1 I just bought. No
hardened valve seats. The previous 2 owners have used STP's Lead Substitute
since tetraethyl lead was phased out of gasoline, 1976 to 1986. Anyone seen
any issue with STP's Lead Substitute? Anyone have good experience with
anything else?

John wrote:
> I've got a completely stock 390 4V in the '69 Mach 1 I just bought. No
> hardened valve seats. The previous 2 owners have used STP's Lead Substitute
> since tetraethyl lead was phased out of gasoline, 1976 to 1986. Anyone seen
> any issue with STP's Lead Substitute? Anyone have good experience with
> anything else?
>